1. Field of the Invention
The present invention relates to artificial implants to replace the male and female human urinary and excretory organs.
One of the principal functions of the urinary and excretory organs is to collect and carry the fluids produced by renal metabolism via the urethras towards the bladder, where those liquids can be stored for a short period. When the liquids reach a certain level and exert a certain pressure on the bladder walls, they are carried to the exit via the urethra, where the operation of a muscle, the sphincter, enables them to be evacuated by acting as a valve.
Replacement of all or a portion of the urinary and excretory organs is indicated, for example, in patients who have undergone a total cystectomy due to cancer of the bladder or a pelvic resection as a result of rectal or cervical cancer. Other indications for this type of replacement are vesicle neurological attacks or interstitial cystitis, tuberculosis, irradiation or schistosomiasis or certain congenital deformities.
2. Description of the Related Art
Only natural implants, using biological material constituted by a variety of organic tissues, essentially intestinal grafts, have until now been able to be used in man without medium term rejection.
However, such biological implants raise a number of problems as regards reflux of liquid, infections, mucous secretions, or as regards absorption of secreted urinary products and ostomal complications.
Such disadvantages have resulted in the development of artificial implants presenting fewer risks than natural biological implants.
A number of models for artificial bladders, ureters, urethras or sphincters comprising a plurality of materials have been separately and experimentally developed for animals but apart from an artificial sphincter, none have been successfully used for a long period of time in humans.
The development of prostheses causing fewer complications after implantation has thus been attempted. Materials tested include vitellium, Teflon.RTM., polyvinyl, Ivalon.RTM., Dacron.RTM., silver, tantalum, as well as expanded polytetrafluoroethylene (Gore-Tex.RTM.).
The majority of materials used have not provided satisfactory results, either because of the rapid development of infections linked to bacterial adhesion to the materials employed, or to the formation of stones, deformation or detachment of the prosthesis, reflux of liquids towards the kidneys, or the rupture of elements of the implant at the anastomoses, the joins between artificial and natural elements.
An ideal material for such an artificial organ intended for implantation inside the human body is one which resists bacterial adhesion. It is also biocompatible so as to be tolerated well by the surrounding tissue and so as not to induce rejection reactions which cause inflammation.
Further, the artificial implant is preferably filled with a small increase in the intraluminal pressure, so as to retain its capacity to refill after emptying and so that it does not collapse.
An additional problem which has to be overcome by using an artificial implant intended to replace portions of the urinary and excretory organs is the reduction in the service life of the implant in situ. This problem is essentially due to fluid leakage (urine being highly corrosive in nature) around the anastomosed connections between the different elements, to the cicatrization of tissue around the prosthesis and more particularly to deposition of detritus contained in urine on the various elements of the prostheses which lead to their deterioration or even obstruction.
One cause of failure as regards the duration of the emplacement of artificial implants results from the use of the materials used above which necessitate periodical replacement of the implanted prosthesis by major surgical intervention, such surgery requiring the anastomoses formed to be destroyed to allow withdrawal.
Silicone gum is known to prevent encrustation of bacteria and constitutes a suitable material for artificial implants which have to come into contact with body fluids over a long period.
However, when artificial silicone bladders were implanted in the abdominal cavity of dogs, with Teflon.RTM. connectors comprising Marlex.RTM. mesh to provide a fibrous function, fluid tight anastomoses were obtained but intestinal complications following rejection due to intolerance of the organism to silicone developed as a result.
An artificial implant intended to replace the bladder should cause neither rejection as a foreign body nor infection nor incrustation nor liquid reflux, nor dilation of higher tracts. Currently, partial replacement of the elements of the urinary system has been disclosed, but the devices used are complex and require sophisticated hydraulic pumping means to control the down-flow of urine and to control bladder emptying.
In this regard, U.S. Pat. No. 5,370,690 by David M Barret discloses an artificial bladder constituted by a rigid outer shell of polysulphone and a flexible inner silicone reservoir. Those two elements delimit between them an open space which can be filled with a biocompatible fluid to a predetermined pressure. The intermediate space is connected to a reservoir and to pumping means which, by exerting pressure, enable the inner reservoir containing urine to be emptied. The device also comprises ureters carrying non-return valves to prevent urine from rising from the bladder towards the kidneys.
The publication "Alloplastic replacement of the urinary bladder" by D. Rohrman et al., in J. of Urology, vol. 156, pages 2094-2097 (1996), describes the replacement of the entire urinary system by a unit constituted by two lateral reservoirs implanted subcutaneously. Problems with fluid reflux from the reservoirs constituting the bladder towards the kidneys subsist, necessitating the installation of two non-return valves in the two catheters connecting the reservoirs to the kidneys.
French patent FR-A-2 255 877 by J. Chevallet and A. Sausse describes a vesical prosthesis which is implantable in the intra-abdominal cavity, which can be connected to ureters and to the urethra of a patient or to prosthetic ureters and/or urethra, which has no artificial valves or flaps, enabling the patient to manually control it.
The device disclosed in that patent comprises a reservoir constituted by a flexible plastics material, preferably a vulcanised elastomer, which gives it the property of returning to its original form after having been deformed by urine being emptied. That device also envisages replacement of the conduits for uretral connections and/or evacuation of urine through the abdominal or perineal wall. Those connections with the remaining natural elements are effected via sleeves of colonisable textile material aimed at encouraging anastomosis to ensure that the implant is held in place.
That device is intended to occupy the position of the natural bladder such that the abdominal muscles contribute to emptying it by exerting a limited pressure. Thus major surgery is required to insert the implant and replace the natural bladder.
In addition to Barret's artificial implant, D. P. Griffith describes a variety of devices in the publication "A prosthetic urinary bladder why not?" in Mayo Clin. Proc. Vol. 67, pp. 293-295, 1992 and emphasises the problems which are not solved by existing implants, namely inflammation caused by inserting artificial tubes into the ureters and/or urethra and liquid tightness problems which occur, in particular at the anastomoses.